Inventory Number: 002704 3rd Edition HFSS Release: 11.1 Published Date: February 20, 2009
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– HFSS is an interactive simulation system whose basic mesh element is a tetrahedron. This allows you to solve any arbitrary 3D geometry, especially those with complex curves and shapes, in a fraction of the time it would take using other techniques. – The name HFSS stands for High Frequency Structure Simulator. Ansoft pioneered the use of the Finite Element Method(FEM) for EM simulation by developing/implementing technologies such as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep(ALPS). Today, HFSS continues to lead the industry with innovations such as Modes-to-Nodes and Full-Wave Spice™. – Ansoft HFSS has evolved over a period of years with input from many users and industries. In industry, Ansoft HFSS is the tool of choice for high-productivity research, development, and virtual prototyping.

– This feature allows you to update any existing Ansoft software from the WebUpdate window. This feature automatically scans your system to find any Ansoft software, and then allows you to download any updates if they are available.

– If you have any questions while you are using Ansoft HFSS you can find answers in several ways: • Ansoft HFSS Online Help provides assistance while you are working. – To get help about a specific, active dialog box, click the Help button in the dialog box or press the F1 key. – Select the menu item Help > Contents to access the online help system. – Tooltips are available to provide information about tools on the toolbars or dialog boxes. When you hold the pointer over a tool for a brief time, a tooltip appears to display the name of the tool. – As you move the pointer over a tool or click a menu item, the Status Bar at the bottom of the Ansoft HFSS window provides a brief description of the function of the tool or menu item. – The Ansoft HFSS Getting Started guide provides detailed information about using HFSS to create and solve 3D EM projects. • Ansoft Technical Support – To contact Ansoft technical support staff in your geographical area, please log on to the Ansoft corporate website, www.ansoft.com and select Contact. • Your Ansoft sales engineer may also be contacted in order to obtain this information.

• Visiting the Ansoft Web Site
– If your computer is connected to the Internet, you can visit the Ansoft Web site to learn more about the Ansoft company and products. • From the Ansoft Desktop – Select the menu item Help > Ansoft Corporate Website to access the Online Technical Support (OTS) system. • From your Internet browser – Visit www.ansoft.com

– The Ansoft HFSS Desktop has several optional panels: • A Project Manager which contains a design tree which lists the structure of the project. • A Message Manager that allows you to view any errors or warnings that occur before you begin a simulation. • A Property Window that displays and allows you to change model parameters or attributes. • A Progress Window that displays solution progress. • A 3D Modeler Window which contains the model and model tree for the active design.

• What is HFSS (High Frequency Structure Simulator)?
– “HFSS is the industry-standard software for S-parameter, full-wave SPICE extraction and electromagnetic simulation of high-frequency and high-speed components. HFSS is widely used for the design of on-chip embedded passives, PCB interconnects, antennas, RF/microwave components, and high-frequency IC packages.” – “HFSS improves engineering productivity, reduces development time, and better assures first-pass design success. The latest release of HFSS delivers significant productivity gains to Microwave/RF engineers and expands electromagnetic co-design to a new segment of engineers working in the areas of RF/analog IC and multi-gigabit designs as well as EMI/EMC.”

– The primary advantage of the FEM for solving partial differential equations lies in the ability of the basic building blocks used to discretize the model to confrom to arbitrary geometry. – The arbitrary shape of the basic building block (tetrahedron) also allows HFSS to generate a coarse mesh where fewer cells are needed to yield an accuate solution, while creating a finely discretized mesh where the field is rapidly varying or higher accuaracy is needed to obtain an accurate global solution.

• The FEM has been a standard for solving electromagnetic problems since the inception of HFSS in 1990.
– The FEM has been a standard for solving problems in structure mechanics since the mid 1950‘s.

• The mesh density is increased where the error is largest. Hence, the final (and computationally most expensive) solution will have a mesh that yields the greatest accuracy with the fewest possible mesh cells.

– The field pattern of a traveling wave inside a waveguide can be determined by solving Maxwell’s equations. The following equation that is solved by the 2D solver is derived directly from Maxwell’s equation.

 1  2 ∇ ×  ∇ × E ( x , y ) − k 0 ε r E ( x , y ) = 0 µ   r 
– where: • E(x,y) is a phasor representing an oscillating electric field. • k0 is the free space wave number, • µr is the complex relative permeability. • εr is the complex relative permittivity. – To solve this equation, the 2D solver obtains an excitation field pattern in the form of a phasor solution, E(x,y). These phasor solutions are independent of z and t; only after being multiplied by e-γz do they become traveling waves. – Also note that the excitation field pattern computed is valid only at a single frequency. A different excitation field pattern is computed for each frequency point of interest.

– It is also possible for a 3D field solution generated by an excitation signal of one specific mode to contain reflections of higher-order modes which arise due to discontinuities in a high frequency structure. – If these higher-order modes are reflected back to the excitation port or transmitted onto another port, the S-parameters associated with these modes should be calculated. – If the higher-order mode decays before reaching any port—either because of attenuation due to losses or because it is a non-propagating evanescent mode—there is no need to obtain the S-parameters for that mode.

• Wave Ports Require a Length of Uniform Cross Section
– Ansoft HFSS assumes that each port you define is connected to a semi-infinitely long waveguide that has the same cross section as the Wave Port

– Isolate part of a structure (i.e. Exciting arbitrary transmission lines)
• Not physically possible to measure in the laboratory • Full-Wave analysis not required for total system – Or total system too complex • Design work/Component level optimization • Post production problem solving
Total System Isolated Component – Via Transition